I have seen this same error message from time to time. The problem was NEVER that the disk was full or that the disk was locked. It was (if memory serves) always due to a faulty path. The smallest things can invalidate the path: failure to append ".pdf" to the filename might do it; a misplaced "/" in the path; and of course, a path to a folder that doesn't exist.

With more testing it seems limited to just two machines that can not write the pdfs. They are set-up as workstations using the same generic logons. It must be the way the machines are set up somehow. I check all the folders I am trying to save into and they have read/write privileges to everyone. I will have to look more into the two machines setup that is blocking things